/**
 * ***************************************************************************** Copyright (c) 2000,
 * 2005 IBM Corporation and others. All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0 which accompanies this
 * distribution, and is available at http://www.eclipse.org/legal/epl-v10.html
 *
 * <p>Contributors: IBM Corporation - initial API and implementation
 * *****************************************************************************
 */
package org.eclipse.jdt.internal.ui.text.template.contentassist;

import org.eclipse.jface.text.BadPositionCategoryException;
import org.eclipse.jface.text.DocumentEvent;
import org.eclipse.jface.text.IPositionUpdater;
import org.eclipse.jface.text.Position;

/**
 * Position updater that takes any change in [position.offset, position.offset + position.length] as
 * belonging to the position.
 *
 * @since 3.0
 */
class InclusivePositionUpdater implements IPositionUpdater {

  /** The position category. */
  private final String fCategory;

  /**
   * Creates a new updater for the given <code>category</code>.
   *
   * @param category the new category.
   */
  public InclusivePositionUpdater(String category) {
    fCategory = category;
  }

  /*
   * @see org.eclipse.jface.text.IPositionUpdater#update(org.eclipse.jface.text.DocumentEvent)
   */
  public void update(DocumentEvent event) {

    int eventOffset = event.getOffset();
    int eventOldLength = event.getLength();
    int eventNewLength = event.getText() == null ? 0 : event.getText().length();
    int deltaLength = eventNewLength - eventOldLength;

    try {
      Position[] positions = event.getDocument().getPositions(fCategory);

      for (int i = 0; i != positions.length; i++) {

        Position position = positions[i];

        if (position.isDeleted()) continue;

        int offset = position.getOffset();
        int length = position.getLength();
        int end = offset + length;

        if (offset > eventOffset + eventOldLength)
          // position comes way
          // after change - shift
          position.setOffset(offset + deltaLength);
        else if (end < eventOffset) {
          // position comes way before change -
          // leave alone
        } else if (offset <= eventOffset && end >= eventOffset + eventOldLength) {
          // event completely internal to the position - adjust length
          position.setLength(length + deltaLength);
        } else if (offset < eventOffset) {
          // event extends over end of position - adjust length
          int newEnd = eventOffset + eventNewLength;
          position.setLength(newEnd - offset);
        } else if (end > eventOffset + eventOldLength) {
          // event extends from before position into it - adjust offset
          // and length
          // offset becomes end of event, length ajusted acordingly
          // we want to recycle the overlapping part
          position.setOffset(eventOffset);
          int deleted = eventOffset + eventOldLength - offset;
          position.setLength(length - deleted + eventNewLength);
        } else {
          // event consumes the position - delete it
          position.delete();
        }
      }
    } catch (BadPositionCategoryException e) {
      // ignore and return
    }
  }

  /**
   * Returns the position category.
   *
   * @return the position category
   */
  public String getCategory() {
    return fCategory;
  }
}
